1. Field of the Invention
The present invention relates to an apparatus and method for transmitting bi-directional optical signals over a single shared optical transmission medium. More particularly, the present invention relates to a novel wavelength division multiplexer (WDM) that facilitates transmission of bi-directional optical signals over a single shared optical transmission medium.
2. Background of the Related Art
Current optical based network systems generally utilize a pair of optical fibers to transmit and receive information from each individual end user station on the optical network. FIG. 1 illustrates an exemplary configuration of an optical based network system, wherein a central network device 11 is in communication with a plurality of end users 12 through individual optical fibers 13 and 14. Upstream optical fibers 13 operate to transmit optical information from end users 12 to network 11, while downstream optical fibers 14 operate to transmit optical information from network 11 to end user 12. Therefore, optical fibers 13 and 14 individually operate to transmit optical information in their respective directions, as indicated by the arrows in optical fibers 13 and 14 in FIG. 1. Although this type of optical network is generally successful in transmitting optical signals at relatively high throughput rates, this configuration suffers from the disadvantage of requiring a substantial supporting infrastructure, as a pair of optical fibers must be routed to each end user 12 in order to allow for bi-directional communication.
Therefore, in view of the clear disadvantages in present optical networking systems, there exists a need for an optically efficient and cost effective apparatus and method for transmitting bi-directional optical signals over a single shared optical transmission medium.